Fluid pump



May 3l, 1960 D. B. KEcEcloGLU ET AL 2,938,468

FLUID PUMP Filed Sept. 13, 1957 United States Patent O rLUm PUMP Dimitri B. Kececioglu, Robert A. Weber, and Norbert Kiefer, Milwaukee, Wis., assignors to Allis-Chalmers Manufacturing Company, Milwaukee, Wis.

Filed Sept. 13, 1957, Ser. No. 683,785

7 Claims. (Cl. 10S-118) This invention relates to rotary pumps or compl'essors and more particularly to a completely enclosed rotary compressor driven by an electric motor which also serves as a compressor rotor coaxially supported for rotation about a centrally disposed stator. Although the present invention will be described in its preferred embodiment as a compressor, its use is not necessarily so limited since it is equally well adapted for use as a tluid pump handling liquids.

Heretofore it has been the usual practice in constructing rotary machines of the radial vane type to make the driving motor unit separate from the driven compressor unit. The motor unit generally is coupled to the compressor shaft to provide the necessary driving torque `for the compressor. According to the practice of the present invention, the compressor and the motor are a single self-contained unit. This arrangement results in effecting a substantial reduction of the number of parts, the total power consumption for a given output, the overall weight, and the space required `for the units. The necessity for aligning and coupling the compressor and motor shaft is eliminated.

The present invention is particularly useful where deleterious gases are pumped by the compressors. Since the present compressor is not driven by a shaft, it is not necessary to provide shaft seals. Any gas leakage through the compressor rotor seals can be entrained in the compresser casing and convenitenly disposed of without contaminating the ambient atmosphere.

In the conventional compressor eiective cooling of the rotor poses a diicult problem. Past solutions to the problems have not been entirely satisfactory. By virtue of the present invention, it is possible to readily cool the rotor of a rotary compressor since the stator is centrally disposed within the rotor and cooling iluid can be circulated through the central stator. Inasmuch as the central stator carries the primary winding, internal cooling of the motor primary winding also is greatly facilitated. As a result, higher compression ratios can be incorporated into the compressor without overheating.

To maintain the efficiency of a radial vane type of compressor as the discharge rate and pressure changes, it is desirable that the radial position of the rotor be readily adjustable in operation. Dueto the fact that the rotors of conventional rotary compressors are driven by a shaft rotatably supported in the housing, the problem of varying the clearance between the bottom of the rotor and the compressor cylinder in operation in order to regulate the discharge pressure and output presents many practical diiculties. Thus, it is highly desirable in a compressor that some means be provided that will readily permit the discharge pressure and output to be eciently regulated, while the compressor is in operation. The compressor construction of the present invention readily permits adjustments to be made to the radial position of the rotor by simply shifting thestator supports.

, In rotary compressors of the prior art considerable ice wear results at the compressor Ivane ends due -to some extent to the reciprocating motion of the rotating vanes.

Excessive end wear causes leakage which reduces compressor eiiiciency. In order to maintain the operating efficientcy at a consistently high level, it is desirable that possible end leakage be eiectively minimized. In the construction embodied in the present invention the end wear is reduced.

It is a general purpose of this invention to provide an improved iluid pump having a centrally disposed motor stator and a coaxially mounted rotor supporting radially slidable vanes.

Another object of this invention is to provide an improved motor driven uid pump comprising a single selfcontained assembly.

A further object of this invention is to provide an improved iiuid pump hvaing a fewer number of parts which are more economical to manufacture and maintain.

A more specific object of this invention is to provide an improved fluid pump which is effectively enclosed and can handle deleterious gases safely by eliminating the necessity for shaft seals communicating with the atmosphere.

Another speciiic object of this invention is to provide an improved sealing means for the rotor ends of a uid pump to prevent leakage from the discharge to the inlet side of the compressor.

It is a further specific object of this invention to provide a means whereby the radial position of the rotor of a fluid pump can be automatically varied to meet the variable pressure and output requirements of a uid system.

It is a still further object of this invention to provide an improved method of mounting sliding vanes in a uid pump rotor to minimize losses due to leakage.

An important object of this invention is to provide an vimproved 4internal cooling system for the driving motor and compressor or fluid pump which permits theunit'to be operated at higher compression ratios without over heating.

Other objects and advantages of this invention are made apparent from the following speciiication by reference to the accompanying drawing wherein.

Fig. 1 is .a longitudinal sectional view of an apparatu according to the present invention; and

Fig. 2 is a transverse sectional view of the apparatus taken along the line II-II of Fig. 1.

Referring to Figs. 1 and 2, a compressor 11 illustrating a preferred embodiment of the present invention has a centrally disposed electric motor 12'. The motor 12 may be of any suitable type but in the preferred embodiment of this invention an inverted squirrel cage induction motor 12 is used. The compressor 11 is a fluid pump of the sliding vane type although it should be readily ap parent that other types of rotary uid pumps may also be used.

Referring to Fig. 1, the squirrel cage induction motor 12 includes primary and secondary windings 13, 14, which are inverted in the preferred embodiment of this invention. What would normally be the armature 'of a conventional squirrel cage induction motor becomes a central stator 16 of the motor 11 and carries the primary winding 13. A rotor l5 carries the secondary winding 14. The central stator 16 has at each end a shaftlike support member 17. Flexible leads 18 from the primary lwinding 13 are brought to a terminal connection 19. The

Patented May 31, 1960 secondary winding 14 on the stator 16 and the primary winding 13 on the rotor 15 even though such an arrangement necessitates the use of slip rings which increases the axial length of the unit.

The stator 16 is of conventional construction and is fabricated of laminations 22 which are keyed to the sup; portmembers 17. A cooling system 23 comprising a series of circumferentially spaced cooling passages 24 is4 provided to cool the stator 16. The cooling passages 24 are lined with a suitable insulating material to provide electrical insulation between the stator laminations 22 and the passage 24. Cooling water enters the system through a central inlet passage 26 provided in the support member 17. The central inlet passage 26 connects with a series of radial passages 27 which are formed integrally with the circumferentially spaced cooling passages 24.

It should be readily apparent to one skilled in the art that since the primary winding 13 does not rotate, the cooling and insulating of the winding 13 are greatly simplified. The type of primary winding used will necessarily depend upon the requirements of a particular application, If multispeed operation is desirable, the primary Winding may be of the type used in a wound rotor induction motor.

The rotor 15 is rotatably supported on the support members 17 by suitable ball bearings 28 capable of taking both radial and axial loading. As shown in Fig. 1, the bearings 28 are lubricated by oil supplied by tube 29. A conventional shaft seal 31 is provided at each bearing 28 to prevent lubricating oil from contaminating the stator winding 13. It should be noted that the oil supplying tube 29 extends into an annular plate 32 secured by a plurality of cap screws to the rotor 1S so that oil can reach the bearings 28. As the rotor 1'5 rotates, centrifugal forces tend to throw the oil outwardly and the pumping action of the end plates 30 assists in returning oil from the bearings 28 to the sump (not shown) and thereby prevents any oil from reaching the high pressure side of the compressor 11.

A compression chamber 33 is formed within a cylinder 34 which serves as a housing for the compressor 11 and motor `12. A central axis 36 of the chamber 33 is disposed eccentrically with respect to an axis 37 of the shaftlike support members 17. The rotor 1S is thereby positioned within the chamber 33 so that its periphery 38 and inner wall 39 of the cylinder 34 dene the crescent shaped volume of the chamber 33. The rotor 1'5 is provided with -a series of circumferentially spaced slotsy 41 which extend longitudinally on the rotor '15. A plurality of blades or vanes 42 are slidingly arranged in the slots 41 for radial movement. The outer longitudinal end faces 43 of the vanes 42 engage the cylindrical wall 39 of the compression chamber 33. The radial end faces 44 of the vanes l43 are closely fitted in radially extending slots 46 formed in the rotor end plate 3i).

v The gas or mixture of gases to be compressed is admitted into an inlet chamber 48 through an inlet opening 49. An outlet 51 is provided and is so arranged so as to communicate with an outlet chamber 52. The outlet and inlet openings 49, l51 are conveniently arranged at opposite sides at the base of the cylinder 34.

The rotor `15 serves a dual function as a compressor and a motor rotor. As hereinbefore described the rotor 15 on its outer periphery 38 performs a iluid displacing function and within its interior carries the secondary winding 14 to perform the function of a rotor of a squirrel cage motor. The rotor 11 is of conventional laminated construction having a series of circumferentially spaced and longitudinally extending slots l53 in which the squirrel cage conductors 54 forming the secondary winding 14 are inserted. At each end an annular ring '56 shorts the squirrel cage conductors l54. The rings '56 are secured by a plurality of cap screws 7. It should be noted that no electrical connections are necessary to energizethe rotor conductors 54. The current generated by the rotor conductors 54 passing through the lines of force of the rotating magnetic eld produced by the stator winding 13 is suicient to create the magnetic field required for the rotor 15.

The cylinder 34 forms the outer casing for the motor and compressor assembly having water passages 60 formed therein for cooling. The cylinder heads 58, 59

g are attached .to the ends of theV cylinder by a plurality of studs 61. As the rotor i15 rotates in a clockwise direction as viewed in Fig. 2, the compressible fluid entering through the inlet 49 will be successively trapped within .the pockets defined by the compression chamber 33. The reduction in volume of the pockets as the rotor 11 revolves causes the fluid to be compressed.

The cylinder vheads 58, 459 are provided with annular grooves 62, 63, respectively. Each groove `62, `63 houses a conventional O ring 64 to seal the clearance between the cylinder heads '58, 59 and the end plates 30. The axial running clearance between the rotor 15 and the cylinder heads '58, y59 is adjusted by two set screws 67, one being disposed in each of the cylinder head end caps 68. The two set screws 67 lock the support members 17 in a lixed axial position to provide the desired running clearance. It should be noted that the running end clearance in the compressor 11 of the present invention is maintained between the rotor end plates 30 and the cylinder heads '58, 59. In the conventional type of radial blade rotary compressor the running clearance is generally maintained between the end of the vanes and the cylinder head. The present arrangement eliminates objectionable wear that takes place at the end of the vanes 42 and also permits an additional seal 64 to be used between the cylinder heads 58, 59 and the rotor 15.

Adjustment to the radial clearances vbetween the rotor 15 and the cylinder 34 are made hydraulically by a piston 69 which when actuated by hydraulic force shift the radial position of the support members 17. The ends of the support members 17 are formed with at surfaces 7l. One end of the actuating pistons 69 is in a thrust transmitting relationship to each of the fiat surfaces 71 of the support members 17. Shifting the position the supporting members 17 radially change the clearance bctween the rotor 15 and the cylinder 34. A bushing 72 serves as a suitable cylinder head for a cylinder 7-4 in which the piston 69 is slidably disposed. Although a hydraulic means for transmitting thrust to change the radial position of the support member is described herein, it is readily apparent that other suitable means for shifting the radial position of the supporting member can he used to adjust the radial clearance of the compressor 11 in accordance with the practice of the present invention.

It should be noted that any variation in the clearance between the rotor 115 and the cylinder '34 will produce a change in the discharge pressure and the output of the compressor.' The arrangement makes it possible to regulate the discharge pressure and the output by adjusting the radial position of the supporting members 17. The adjustments can be made manually or automatically by a pressure responsive means controlling a pump (not shown), which supplies hydraulic pressure to actuate the piston 69.

An important feature of the fluid pump which is the subject of the present invention is that the driving unit and the compressor unit are completely enclosed by a housing comprising the cylinder 34, the two cylinder heads 58, l59 and the end caps 68. The vertical joints between the cylinder '34 and the cylinder heads 58, 59 are sealed by a gasket 77. A significant feature of the `present construction is that there is no rotating shaft extending through compressor housing as would normally be encountered in a conventional type of rotary compressor. This feature makes it possible for the unit to safely handle deleterious gases and also permits the unit to be operated completely submerged, if desired.

Toprovid'e adequatea'nd positive lubrication for the vanes 42 in thema-f dos 41, raaiauy extending @i1 passages 78 are formed in Vthe cylinder 34. The passages 78.provide for the direct delivery of oil to the vanes 42 at two intermediate points longitudinally spaced between the ends of the vanes 42. As the vanes 42 move outwardly in the slots 41, oil entering through the radial passage 78 drips on the vanes 42.- After the vanes 42 move past the inlet opening 49 and are forced back into the slots 41, the oil is worked into the slots 41 by the sliding movement of the vanes 42. Part of the oil is also thrown outwardly by centrifugal force. This oil lubricates the vanes between their longitudinal ends 43 and the interior wall 39 of vthe cylinder 34. A series of circumferentially spaced radial passages 79 formed in the cylinder .heads 58, 59 are provided to lfurnish direct lubrication to two wearing rings 81. The sealing ring =64 prevents the oil from entering into a chamber 82 :formed by the cylinder heads 58, 59 and the end caps L68. The oil supplied to lubricate the compressor vanes \42, the wearing rings 81 and the bearings 28, drains byl ;gravity to a sump (not shown) where it is collected ;and recirculated.

,The compressor is operated like any other conventional xmotor driven unit. To start the compressor a motor switch or controller (not shown) is operated to supply .electric current to the stator windings. The current passlling' through the stator windi-ngs 13 sets up a rotating magnetic eld. As 4this magnetic eld swings around within the stator structure, it cuts the heavy copper bars 54V imbedded in the surface of the rotor 15. Currents will thereby be induced in the bars 54, and these curvrents set up a magnetic eld around and within the rotor '15. Due to the interaction between the rotor and stator vmagnetic fields, the rotor 15 will then begin to rotate. It should be noted that'a very small starting torque is required because the vanes 42 do not extend outwardly to compress or pump until the motor 12 reaches a sufficient speed so that the centrifugal forces are of sufficient magnitude `to .maintain the vanes 42 in an extended .position Thus, the initial starting torque need only fovercome the inertia of the rotor 15.

At the normal operating speed of the motor 12, the .rotor 15 rotates at a speed such that the vanes 42 are vurged against the wall 39 of the cylinder 34. Since the rotor 15 rotates in an eccentric relationship with respect to the cylinder wall 39, the vanes 42 cooperate with the `cylinder wall 39 to define chambers of Variable volume. If the machine is used as a compressor, these chambers 'or 'pockets carry the air or other gas from one pressure .to 'ahigher pressure. When the machine is utilized as a vacuum pump, the air or other gas is carried from one 'pressure to a lower pressure.

, When functioning as a compressor, the air or gas is drawn at substantially atmospheric pressure to inlet chamber 48 and is delivered at a higher pressure into the out- ',let chamber 52. The compressing operation results in ythe evolution of a considerable amount of heat in the air or gas being compressed. Some of heat energy is absorbed by the cylinder wall 39 and the rotor 15. The cylinder 34 is maintained at a substantially uniform temperature by the water jacket yformed by the passages 60. In the preferred embodiment of this invention a liquid cooling system is provided for the stator winding 13. In addition to carrying out any excess heat generated by the winding 13, it also carries away some of the heat of compression.

When it is desired to vary the outlet pressure and discharge rate, hydraulic pressure is supplied to .the two actuating pistons 69 to adjust the radial position of the support members 17. As the radial position of the support members 17 is varied, the eccentric relationship between the rotor 15 and the cylinder 34 changes and accordingly the minimum and the maximum volumes of the compression pockets formed by the rotary vanes 42 also vary. If the support members 17 are raised, it is readily seen that the discharge pressure is decreased.

'From the foregoing it will be seen that the present invention provides a -novel combination of a compressor and a driving motor having a centrally `disposed stator and a coaxially mounted rotor mounting a rotary compressor. The necessity of a shaft seal is thereby eliminated and the compressor and driving motor can be completely enclosed.

While only one particular embodiment of the applicants invention has been described herein, it should be understood that the applicants invention is not restricted thereto and that it is intended to cover all modiiications of the invention which would be apparent to one skilled in `the art and that come within the scope of the appended claims.

What is claimed is:

l. A rotary machine of the sliding vane Itype comprising: a casing defining an inner cylindrical surface centered about a first axis and presenting a pair of axially spaced annular grooves; a rotor having a hollow central core and supported at each end within said casing for rotation about a second axis parallel to and radially spaced from said first axis, said rotor having a plurality of slots formed in the outer periphery and a plurality of vanes slidably disposed therein and sealingly engaging said inner cylindrical surface; a plate carrying each end of said rotor and extending radially therefrom into the adjacent of said annular grooves; sealing means interposed between each of said plates and said grooves preventing the passage of duid therebetween; an electric motor having a primary and a secondary winding; a stator centrally disposed within said core and carrying one of said windings, the other of said windings being operatively disposed in said rotor; and a shaftlike extension at each end vof said stator rotatably supporting said end plate and nonrotatably supported by said casing.

2. In a rotary machine of the sliding vane type having apcasing formed with an internal cylindrical surface ccn- "tered about a rst axis and presenting a pair of axially spaced annular grooves, a rotor having a hollow core centrally disposed about a second axis parallel with and radially spaced from said rst axis, and a plurality of slots formed in the outer periphery of said Vrotor and slidably mounting a plurality of vanes sealingly engageable with said inner cylindrical surface, the improvement comprising: a plate radially extending from each end of said rotor into said annular groove, a sealing means interposed between each of said plates and grooves to vprevent uid leakage, a motor having a primary and a secondary winding; a stator operatively carrying one of said windings and being centrally disposed within said core about said second axis; the other of said windings of said electric motor being operatively disposed in said rotor; a support extension formed at each end of said stator, and means provided in said casing to support and selectively vary the radial position of said support extension inorder to change the radial spacing between said rotor and said cylindrical surface.

3. In a rotary machine of the sliding vane type having a casing defining an internal cylindrical surface cen tered about a first longitudinal axis, a rotor having a hollow core centraily disposed about a second longitudinal axis parallel with and radially spaced from said rst axis, an end plate supporting said rotor at each end for rotation about said second axis, the improvement comprising: an annular groove formed in said casing at each end of said cylindrical surface; a plate carrying each end of said rotor and extending radially therefrom into an adjacent one of said annular grooves; sealing means interposed between each of said plates and said grooves preventing the passage of iiuid therebetween; an electric motor having a primary and -a secondary winding; a stator centrally disposed within said core, one. of said Windings of said motor being operatively disposed in said stator and said rotor; a support extension at each end of said stator; a plurality of cooling passages formed within said stator to remove excess heat; a supply pat-V asesina sage-formed in said support extension at one end of said stator and connecting with said cooling passagesva r e turn passage lformed in the support extension at the other eidof said stator and connecting with said cooling passages to return the cooling fluid Yfrom said stator, said support extensions being nonrotatably supported within said casing and selectively adjustable to vary the radial position between said rotor and said cylindrical surface.

4. `In a rotary machine of the sliding vane type having a casing `formed with an internal cylindrical surface centered about a rst axis and presenting a pair of axially spaced annular grooves, a rotor having a hollow core centrally disposed about a second axis parallel with and radially spaced from said first axis, and a plurality of slots formed in the outer periphery of said rotor and slidably mounting a plurality of vanes sealingly engageabl'e .with said inner cylindrical surface, the improvement comprising: a plate radially extending from each end of said rotor into said annular groove; sealing means interposed between each of said plates and grooves to prevent uid leak-age therebetween; a stator centrally disposed within said core about said second axis; an electric motor having a primary and a secondary winding, `said primary Winding being carried by said stator and said secondary winding being operatively disposed `in said rotor; a support extension formed at each end of said stator; and means provided in said casing to support and selectively vary the radial position of said support extension in order totchange the radial spacing between said rotor and said cylindrical surface.

5,. A rotary machine of .the sliding vane type comprising: a casing dening an inner cylindrical surface centered about a first axis and presenting a pair of axially spaced annular grooves; -a rotor having a hollow central core and supported at each end within said casing for `rotation about a second .axis in spaced parallel relationship to said rst axis, said rotor having a plurality of 4slots formed in the outer `periphery thereof and a plu- -ralty of vanes slidably `disposed therein and sealingly engaging said inner cylindrical surface; a plate carrying each end `of said rotor and extending radially therefrom into the adjacent one of said annular grooves; sealing means interposed between each of said plates and said grooves to prevent fluid leakage therebetween; a stator 4centrally disposed within said core; an .electric motor having a primaryand a secondary winding, said primary winding being carried by said stator and said secondary ywinding being voperatively disposed in said rotor; and a shaftlike extension at each end of said stator rotatably vsupporting said end plate and nonrotatably supported by groove formed in said. casing at each end of said cylindrical surface; andv end vplate radially extending from each end of said rotor into said annular groove; sealing means interposedbetween each of said plates and grooves to prevent fluid leakage therebetween; a stator centrally disposed within said core; an electric motor having a primary and a secondary winding, said primary winding being operatively disposed in said stator and said secondary winding being operatively disposed in said rotor; and a support extension at each end of said stator being nonrotatably supported Within said casing and selectively adjustable to vary the radial position between said rotor and said cylindrical surface.

7. -A rotary machine comprising: a casing having an internal surface defining a cylindrical chamber axially disposed about a rst axis and having a pair of axially spaced annular grooves defined therein, one being adjacent each end thereof; a rotor supported within said casing and having a hollow core axially disposed about a second axis in spaced parallel relationship to said trst axis; a stator carried by said casing and centrally disposed within said core, said stator having a plurality of circumferentially spaced longitudinally extending slots formed in the outer periphery thereof; a pair of end plates, one each being interposed between an end o f said rotor and said casing for carrying said rotor and projecting radially therefrom into sealing engagement in .said annular grooves, each of said plates having a plurality of spaced radially extending slots corresponding to said slots in said rotor; a plurality of vanes slidably mounted in said rotor slots and in said end plate slots to sealingly engage said internal surface of said chamber;

Vand an electric motor having a primary and a secondary winding, one of said windings being carried by `said stator while the other of said windings is carried by said rotor.

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